This invention relates generally to a load handling vehicle. More particularly, this invention relates to a vehicle designed to carry long and heavy loads in relatively narrow aisles, and which has the ability to travel at right angles to the direction of travel for stacking purposes.
Currently there is a great demand in industry for a vehicle capable of handling heavy loads. Users of such loader vehicles include: the building industry; the logging industry; steel mills; miscellaneous fabrication plants; ship terminals; airports; and many other facilities. The loader vehicle has special application to the transporting and stacking of containers, such as ISO (International Standards Organization) containers used extensively to ship a wide variety of goods on multiple modes of transportation, such as ships, trucks, trains, planes, etc.
It may be parenthetically noted that while this disclosure talks mainly in terms of loads in the form of containers, such is merely for the sake of convenience. One of the principal applications of the inventive loader vehicle would be to transport containers. The loader vehicle would also be suited to carry other long and heavy loads. For example, loads such as logs, lumber, pipe, rolled steel, concrete and steel beams, and laminated wood beams would also be within the purview of the load type capability of the subject vehicle. It is contemplated that various load holding means such as grapples might be substituted for the normal forks, depending on the particular load.
In industry today there is a general disadvantage of lack of versatility of container or other load handling vehicles. That is, special purpose machines have had to be built for narrow aisle applications, rather than having a universal or multi-purpose loader vehicle. No single machine or loader vehicle has been capable of performing all of the multitude of jobs, for example, in high density and volume container marshalling yards while utilizing yard space to a higher degree than is presently possible.
Some of the prior art devices include conventional side loaders, straddle carriers, and cranes. Examples of some of these devices may be found by having reference to U.S. Pat. No. 3,586,183 to Shaffer and U.S. Pat. No. 3,669,290 to Doyle, both assigned to the Assignee hereof. Other examples may be found in U.S. Pats. No. 2,773,612 to West et al and 2,996,206 to McKee.
Where operating room permits the use of wide aisles, and operator visibility and load and vehicle stability are not problems, long loads are often carried on conventional lift truck vehicles. U.S. Pat. No. 3,207,249 to Singer et al is exemplary of such a lift truck vehicle.
The above-described loader vehicles have not proven to be entirely satisfactory for various reasons. With the standard lift truck, very long containers, e.g. 40 foot, require that the load be carried cross-wise. This necessitates corresponding 40 foot wide-plus aisles, which are not the most economic utilization of storage space. In addition, 40 foot wide containers carried cross-wise are difficult to maneuver.
Straddle carriers, both stacking and non-stacking, are preferable to lift trucks and are perhaps the most popular means for handling containers. These straddle carriers can negotiate aisles with containers in end-wise relation, thus requiring aisles only slightly wider than the typical 8 foot container width. However, these straddle carriers do have their limitations. For instance, as the need for greater storage density increases in importance, one of their limitations is met. Straddle carriers must "circus load", which refers to the characteristic need to enter a row always from an end. The straddle carrier is unable to select or deposit a load at random positions within a row without traveling in from one end. The exit mode is similarly restricted with straddle carriers.
Conventional side loaders also suffer from deficiencies. While they can meet the requirement of higher storage density by block stacking, i.e. stacking containers on top of each other in tiers, they have limitations in their selectivity in retrieval. They also have limitations in load capacity in the upper storage tiers. That is, they have limitations in the weight of containers or loads that they can successfully stack.